Remuxing give different bitrate for video

I'm new to REMUXing. I use mkvmergeGUI (only) and add the M2TS stream that I wanted, then I select only the video, audio, subtitle stream I want, and start MUXING.

The result gives me a files with different video bitrate (using MediaInfo). The data is below.

Is this normal, I thought its supposed to be LOSSLESS, and thus bitrate would be preserved.


FROM M2TS
Format : BDAV
Format/Info : Blu-ray Video
File size : 34.6 GiB
Duration : 2h 49mn
Overall bit rate mode : Variable
Overall bit rate : 29.2 Mbps
Maximum Overall bit rate : 48.0 Mbps
Video
ID : 4113 (0x1011)
Menu ID : 1 (0x1)
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4.1
Format settings, CABAC : Yes
Format settings, ReFrames : 2 frames
Codec ID : 27
Duration : 2h 49mn
Bit rate mode : Variable
Bit rate : 25.1 Mbps
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.504
Stream size : 29.7 GiB (86%)

REMUX FILE
Overall bit rate : 26.2 Mbps
Encoded date : UTC 2013-03-12 11:57:04
Writing application : mkvmerge v6.1.0 ('Old Devil') built on Mar 2 2013 14:32:37
Writing library : libebml v1.3.0 + libmatroska v1.4.0
Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4.1
Format settings, CABAC : Yes
Format settings, ReFrames : 2 frames
Codec ID : V_MPEG4/ISO/AVC
Duration : 2h 49mn
Bit rate mode : Variable
Bit rate : 24.1 Mbps
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.484
Stream size : 28.5 GiB (92%)
Default : Yes
Forced : Nothanks in advance,